learn: Learn
In grnn: General regression neural network

Create or update a General regression neural network.

1	learn(set, nn, variable.column = 1)

`set`	Data frame representing the training set. The first column is used to define the category of each observation (set `category.column` if it is not the case).
`nn`	A General regression neural network with or without training.
`variable.column`	The field number of the variable (1 by default).